1. Field of Invention
The present invention relates to frequency-controlled inverters having tuned L-C output circuitry, particularly of a kind wherein control of frequency provides control of output power in such manner as to compensate for effects of variations in the magnitude of the DC supply voltage.
2. Elements of Prior Art
In conventional inverter-type power supplies, especially in connection with fluorescent lamp ballasts, in order to attain a low crest factor of the output current, it is necessary to power the inverters from a DC supply voltage having little or no ripple.
In many applications of power-line-operated inverter-type power supplies, in order to draw power from the power line with a relatively high power factor, it is necessary to permit the inverter's DC supply voltage to exhibit a relatively high degree of ripple.
Thus, in conventional power-line-operated inverter-type power supplies, especially in case of fluorescent lamp ballasts, there is a basic conflict between drawing power from the power line with a high power factor and at the same time providing an output current having a low crest factor.
To resolve this conflict, various forms of relatively complex power factor correction schemes are being used. These various power factor correction schemes function such as to cause power to be drawn from the power line with a relatively high power factor while at the same time providing a substantially constant-magnitude DC supply voltage.